2026: OpenSCAD robot and remote, physical joint limits, model in Unity

hardware/openscad/ rebuilds the broken Fusion models as OpenSCAD: body (top/bottom plate, standoffs, battery bay, switch), legs (coxa bracket, femur link, tibia, horn adapters, TPU socks, servo cables), the whole robot, and the remote (shell, lid, Nextion 3.5", JH-D400X-R4 sticks, 18650 UPS board, IMU, Teensy 4.0, USB-C breakout). Every part was checked by slicing against the original STEP solids; the original's bugs are fixed and listed in PLANNING.md. The robot now uses a hexagon leg layout (corner legs 60 deg round from the mid legs; the corner coxa brackets need turning on their splines). Physical limits from a collision sweep of the model are in Config.h: per-leg coxa limits and LEG_CLEARANCE_MM 56 (a leg is 55.2 mm wide at the joints); the sim API exports them (version 7). sim_smoke passes. Unity loads the model (export_unity.py -> Resources/OpenScadModel, OpenScadModel.cs builds a new rig in place of the old scene's robot). The PCB model's mounting holes now use the exact EasyEDA grid. README shows renders of both. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-14 12:14:32 +01:00
1 parent b1c94e4149
commit 91b5b99fd5
@@ -37,3 +37,4 @@
 *.ide-wal filter=lfs diff=lfs merge=lfs -text
 *.ide-shm filter=lfs diff=lfs merge=lfs -text
 2018-unity-sim/**/*.unity filter=lfs diff=lfs merge=lfs -text
 *.bytes filter=lfs diff=lfs merge=lfs -text
@@ -168,6 +168,11 @@ Remote stick-frame convention: logical X + = right, Y + = forward, twist +
  - `HexapodSimBootstrap` auto-adds `HexapodSimulation` in any scene and
    disables the old scripts (`Walk`, `RotationControl`, `Leg`,
    `HandleHoystick`). Those are kept for reference only.
  - `OpenScadModel` replaces the old scene's robot with the OpenSCAD model
    (meshes from `hardware/openscad/export_unity.py` in
    `Resources/OpenScadModel/`): it builds a new rig with the same names at
    the Config.h geometry, whose rest pose (coxa 0, femur 0, tibia -90) is
    the zero rotation. `HexapodSimulation.useOpenScadModel` turns it off.
  - `HexapodSimNative` loads a temp copy of the DLL via
    LoadLibrary/GetProcAddress, so there's no file lock and each Play is a
    fresh power-on.
@@ -212,14 +217,25 @@ Robot (`robot/README.md` has detail):
 - `Config.h` geometry now comes from the Unity model (owner's request),
  1 unit = 10 mm:
  - legs at X ±100 / 0, Y ±50 / ±65 mm,
-  - mount angles ±90° (coxa straight sideways at servo center),
+  - mount angles ±30° / ±90° / ±150° (hexagon layout, owner's request: mid
    legs sideways, corner legs 60° further round; coxa direction at servo
    centre — the corner brackets sit 60° round on their splines),
  - coxa/femur/tibia 55/100/150 mm,
  - stance radius 75 (so 130 mm out from the coxa pivot), height 150 mm.
  The old scene's `Leg.translateX` = ±5 was only the old code's rotation
  pivot; the rig hips are at x ±10. Still to confirm on the real chassis:
-  joint limits, servo pins, µs/deg calibration, `MAX_JOINT_DEG_S` (in
+  servo pins, µs/deg calibration, `MAX_JOINT_DEG_S` (in
  robot.ino), the Limits envelope, InputMapper maxima.
 - **Geometry and limits confirmed against the CAD (owner's request):** the
  OpenSCAD rebuild of the real chassis (`hardware/openscad/`, see its
  `PLANNING.md`) has exactly these mounts and 55/100/150 mm links (tibia to
  the centre of a 10 mm foot ball; femur/knee axes in the coxa pivot plane,
  13.5 mm above the bottom plate). Its collision sweep gave the joint
  limits now in `Config.h`: coxa limits are **per leg**
  (`COXA_MIN_DEG[i]`/`COXA_MAX_DEG[i]`; all ±60 in the hexagon layout, but in
  the old sideways layout a corner leg only swung ~36° towards its mid leg),
  and `LEG_CLEARANCE_MM` is 56 (a leg is 55.2 mm wide at the joints). The sim API exports the per-leg coxa limits (version 7).
 - **Fixed (owner-approved):** the `Kinematics.cpp` femur elevation sign
  (`atan2(local_z, horiz)`; it used to solve for a foot above the hip, so
  every solution was invalid). Stance pose is now femur −1.2°, tibia
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@@ -0,0 +1,75 @@
 using System.IO;
 using UnityEditor;
 using UnityEditor.SceneManagement;
 using UnityEngine;
 namespace HexapodSim
 {
    // Batch-mode check of the OpenSCAD model in Main.unity, without entering
    // Play mode: builds the model from the DLL's geometry, poses the legs in
    // the firmware's standing pose and renders the main camera to PNGs.
    //   Unity.exe -batchmode -projectPath . -executeMethod HexapodSim.OpenScadModelSnapshot.Run
    //             -snapshotDir <folder> -quit
    public static class OpenScadModelSnapshot
    {
        public static void Run()
        {
            string dir = Arg("-snapshotDir") ?? Path.GetFullPath("Temp/OpenScadSnapshot");
            Directory.CreateDirectory(dir);
            EditorSceneManager.OpenScene("Assets/Main.unity");
            Transform chassis = null;
            foreach (var t in Object.FindObjectsByType<Transform>())
                if (t.name == "Leg" && t.Find("hip1") != null) { chassis = t.parent; break; }
            if (chassis == null) { Debug.LogError("[Snapshot] no leg rig in Main.unity"); EditorApplication.Exit(1); return; }
            string dll = Path.GetFullPath(Path.Combine(Application.dataPath, "..", "..", "sim", "build", "hexapod_sim.dll"));
            HxGeometry g;
            using (var native = HexapodSimNative.Load(dll)) g = native.Geometry;
            OpenScadModel.Build(chassis, g, ForwardAxis.NegativeX, 0.1f);
            // Firmware stance: coxa 0, femur -1.2, tibia -98.3 (HexapodSimulation.ApplyJoints).
            foreach (Transform leg in chassis)
            {
                if (leg.name != "Leg" || !leg.gameObject.activeSelf) continue;
                var hip2 = leg.Find("hip1/Hip2");
                var knie = leg.Find("hip1/Hip2/Knie");
                hip2.localRotation = Quaternion.Euler(1.2f, 0, 0);
                knie.localRotation = Quaternion.Euler(-(-98.3f + 90f), 0, 0);
            }
            var cam = Camera.main;
            if (cam == null) cam = new GameObject("SnapshotCamera").AddComponent<Camera>();
            Vector3 c = chassis.position;
            Shoot(cam, c + new Vector3(-30, 22, -38), c, Path.Combine(dir, "front_left.png"));
            Shoot(cam, c + new Vector3(42, 30, 20), c, Path.Combine(dir, "rear_right.png"));
            Shoot(cam, c + new Vector3(0.01f, 60, 0), c, Path.Combine(dir, "top.png"));
            Debug.Log("[Snapshot] wrote " + dir);
            EditorApplication.Exit(0);
        }
        static void Shoot(Camera cam, Vector3 pos, Vector3 target, string file)
        {
            cam.transform.position = pos;
            cam.transform.LookAt(target);
            cam.fieldOfView = 45;
            var rt = new RenderTexture(1280, 900, 24);
            cam.targetTexture = rt;
            cam.Render();
            RenderTexture.active = rt;
            var tex = new Texture2D(rt.width, rt.height, TextureFormat.RGB24, false);
            tex.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0);
            tex.Apply();
            File.WriteAllBytes(file, tex.EncodeToPNG());
            cam.targetTexture = null;
            RenderTexture.active = null;
        }
        static string Arg(string name)
        {
            var a = System.Environment.GetCommandLineArgs();
            for (int i = 0; i < a.Length - 1; i++) if (a[i] == name) return a[i + 1];
            return null;
        }
    }
 }
@@ -0,0 +1,2 @@
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@@ -36,7 +36,9 @@ namespace HexapodSim
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)] public float[] mountAngleDeg;
        public float coxaMm, femurMm, tibiaMm;
        public float stanceRadiusMm, stanceHeightMm;
-        public float coxaMinDeg, coxaMaxDeg, femurMinDeg, femurMaxDeg, tibiaMinDeg, tibiaMaxDeg;
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)] public float[] coxaMinDeg;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)] public float[] coxaMaxDeg;
        public float femurMinDeg, femurMaxDeg, tibiaMinDeg, tibiaMaxDeg;
        public float controlHz;
        public float legClearanceMm;
        public float stanceHeightRangeMm;
@@ -71,7 +73,7 @@ namespace HexapodSim
    // "Reload firmware" and the new code runs. Each load is a fresh power-on.
    public sealed class HexapodSimNative : IDisposable
    {
-        public const int ExpectedApiVersion = 6;   // HXSIM_API_VERSION
+        public const int ExpectedApiVersion = 7;   // HXSIM_API_VERSION
        [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate int IntFn();
        [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate void VoidFn();
@@ -32,6 +32,9 @@ namespace HexapodSim
        public float unitsPerMm = 0.1f;
        [Tooltip("Firmware tibia angle when the rig's Knie rotation is 0 (tibia straight down from a horizontal femur).")]
        public float kneeRestDeg = -90f;
        [Tooltip("Replace the old scene's robot with the OpenSCAD model (hardware/openscad, export_unity.py).")]
        public bool useOpenScadModel = true;
        bool openScadBuilt_;
        [Header("World")]
        [Tooltip("Tilts the ground (deg about robot X = roll, Y = pitch) to exercise the robot gyro.")]
@@ -123,6 +126,11 @@ namespace HexapodSim
                Native.SetRadioPresent(radioPresent);
                Native.SetImuPresent(imuPresent);
                Geometry = Native.Geometry;
                if (useOpenScadModel && !openScadBuilt_ && OpenScadModel.Available)
                {
                    OpenScadModel.Build(chassis, Geometry, forwardAxis, unitsPerMm);
                    openScadBuilt_ = true;
                }
                BindRig();
                Native.SetGroundTilt(groundTiltDeg.x, groundTiltDeg.y);
                Native.Start();
@@ -0,0 +1,140 @@
 using System.Collections.Generic;
 using System.IO;
 using UnityEngine;
 using UnityEngine.Rendering;
 namespace HexapodSim
 {
    // Swaps the old scene's robot for the OpenSCAD model (hardware/openscad,
    // exported by export_unity.py into Resources/OpenScadModel). Builds a new
    // rig under the same chassis with the names HexapodSimulation looks for
    // (Leg > hip1 > Hip2 > Knie, plus the Point foot marker), with its pivots
    // exactly at the Config.h geometry, and hides the old visuals. The meshes
    // are in the rest pose (coxa 0, femur 0, tibia -90), which is the rig's
    // zero rotation, so the existing joint driving moves them correctly.
    public static class OpenScadModel
    {
        const string Folder = "OpenScadModel/";
        public static bool Available => Resources.Load<TextAsset>(Folder + "body") != null;
        public static void Build(Transform chassis, HxGeometry g, ForwardAxis f, float unitsPerMm)
        {
            Material template = null;
            foreach (var r in chassis.GetComponentsInChildren<Renderer>(true))
            {
                if (template == null && r.sharedMaterial) template = r.sharedMaterial;
                r.enabled = false;
            }
            foreach (var t in Object.FindObjectsByType<Transform>())
                if (t.name == "Leg" && HasChild(t, "hip1")) t.gameObject.SetActive(false);
            var shader = Shader.Find("Standard") ?? (template ? template.shader : null);
            AddMesh(chassis, "OpenSCAD body", Folder + "body", Quaternion.identity, f, unitsPerMm, shader);
            for (int i = 0; i < g.numLegs; i++)
            {
                string side = g.mountAngleDeg[i] > 0 ? "left" : "right";
                float a = g.mountAngleDeg[i] * Mathf.Deg2Rad;
                var root = new GameObject("Leg").transform;
                root.SetParent(chassis, false);
                root.localPosition = RobotFrame.ToUnity(new Vector3(g.mountXmm[i], g.mountYmm[i], 0), f) * unitsPerMm;
                root.localRotation = Quaternion.LookRotation(
                    RobotFrame.ToUnity(new Vector3(Mathf.Cos(a), Mathf.Sin(a), 0), f), Vector3.up);
                // The meshes are exported as a leg pointing straight sideways (mount
                // +90 left, -90 right) in chassis axes; in the joint's own frame that
                // is the same for any mount angle.
                float refRad = (side == "left" ? 90f : -90f) * Mathf.Deg2Rad;
                Quaternion toJoint = Quaternion.Inverse(Quaternion.LookRotation(
                    RobotFrame.ToUnity(new Vector3(Mathf.Cos(refRad), Mathf.Sin(refRad), 0), f), Vector3.up));
                var hip1 = Child(root, "hip1", Vector3.zero);
                AddMesh(hip1, "coxa", Folder + $"leg_{side}_coxa", toJoint, f, unitsPerMm, shader);
                var hip2 = Child(hip1, "Hip2", new Vector3(0, 0, g.coxaMm * unitsPerMm));
                AddMesh(hip2, "femur", Folder + $"leg_{side}_femur", toJoint, f, unitsPerMm, shader);
                var knie = Child(hip2, "Knie", new Vector3(0, 0, g.femurMm * unitsPerMm));
                AddMesh(knie, "tibia", Folder + $"leg_{side}_tibia", toJoint, f, unitsPerMm, shader);
                // Where the firmware's FK puts the foot (centre of the foot ball).
                var marker = GameObject.CreatePrimitive(PrimitiveType.Sphere);
                var collider = marker.GetComponent<Collider>();
                if (Application.isPlaying) Object.Destroy(collider); else Object.DestroyImmediate(collider);
                marker.name = "Point";
                marker.transform.SetParent(knie, false);
                marker.transform.localScale = Vector3.one * 4f * unitsPerMm;
                marker.GetComponent<Renderer>().material = MakeMaterial(shader, new Color(0.9f, 0.1f, 0.1f));
            }
        }
        static bool HasChild(Transform t, string name)
        {
            foreach (Transform c in t)
                if (string.Equals(c.name, name, System.StringComparison.OrdinalIgnoreCase) || HasChild(c, name)) return true;
            return false;
        }
        static Transform Child(Transform parent, string name, Vector3 localPos)
        {
            var t = new GameObject(name).transform;
            t.SetParent(parent, false);
            t.localPosition = localPos;
            return t;
        }
        static Material MakeMaterial(Shader shader, Color c)
        {
            var m = new Material(shader) { color = c };
            if (m.HasProperty("_Glossiness")) m.SetFloat("_Glossiness", 0.25f);
            return m;
        }
        // Reads one export_unity.py file: robot-frame mm, pivot-relative,
        // counter-clockwise outward winding (right-handed). RobotFrame.ToUnity is a
        // reflection, so every triangle is flipped to stay front-facing.
        static void AddMesh(Transform parent, string name, string resource, Quaternion toLocal,
                            ForwardAxis f, float unitsPerMm, Shader shader)
        {
            var asset = Resources.Load<TextAsset>(resource);
            if (asset == null) { Debug.LogWarning($"[HexapodSim] missing model mesh {resource}"); return; }
            var verts = new List<Vector3>();
            var groups = new List<int[]>();
            var mats = new List<Material>();
            using (var br = new BinaryReader(new MemoryStream(asset.bytes)))
            {
                if (new string(br.ReadChars(4)) != "HXM1") { Debug.LogWarning($"[HexapodSim] {resource}: not a model mesh"); return; }
                int n = br.ReadInt32();
                for (int k = 0; k < n; k++)
                {
                    var col = new Color(br.ReadSingle(), br.ReadSingle(), br.ReadSingle(), br.ReadSingle());
                    int tris = br.ReadInt32();
                    var idx = new int[tris * 3];
                    for (int t = 0; t < tris; t++)
                    {
                        int b0 = verts.Count;
                        for (int v = 0; v < 3; v++)
                        {
                            var r = new Vector3(br.ReadSingle(), br.ReadSingle(), br.ReadSingle());
                            verts.Add(toLocal * (RobotFrame.ToUnity(r, f) * unitsPerMm));
                        }
                        idx[t * 3] = b0; idx[t * 3 + 1] = b0 + 2; idx[t * 3 + 2] = b0 + 1;
                    }
                    groups.Add(idx);
                    mats.Add(MakeMaterial(shader, col));
                }
            }
            var mesh = new Mesh { name = name, indexFormat = IndexFormat.UInt32 };
            mesh.SetVertices(verts);
            mesh.subMeshCount = groups.Count;
            for (int k = 0; k < groups.Count; k++) mesh.SetTriangles(groups[k], k);
            mesh.RecalculateNormals();
            mesh.RecalculateBounds();
            var go = new GameObject(name);
            go.transform.SetParent(parent, false);
            go.AddComponent<MeshFilter>().sharedMesh = mesh;
            go.AddComponent<MeshRenderer>().sharedMaterials = mats.ToArray();
        }
    }
 }
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@@ -3,12 +3,16 @@
 A six-legged walking robot (Teensy 3.6) and its handheld remote
 (Teensy 4.1 + Nextion touchscreen), linked over nRF24L01.
 ![The hexapod, OpenSCAD model in its standing pose](hardware/openscad/renders/hexapod.png)
 ![The remote, OpenSCAD model](hardware/openscad/renders/remote.png)
 ```
 robot/                     robot firmware: IK, gait, body pose, IMU stabilization, state machine
 remote/                    remote firmware: 2 x 3-axis sticks, MPU6050 tilt, Nextion UI, RF24 TX
 shared/                    HexapodProtocol: the CmdPacket wire format + radio settings used by both
 sim/                       the unchanged robot firmware compiled into a DLL for the simulation
 Hexapod_Simulation_Unity/  Unity project that runs that DLL on the 3D model
 hardware/openscad/         OpenSCAD model of the robot and remote, rebuilt from the Fusion designs
 hardware/fusion360/        Fusion 360 designs: body, legs, servo, servo horn, remote case
 scripts/                   PlatformIO helper (per-environment sketch folder)
 ```
@@ -68,8 +68,9 @@ y_mm = (3330.7087 - y_eda) * 0.254
 - Outline: 46.0 × 89.0 mm, black soldermask, 1.6 mm FR4 (the OBJ's 2.54 mm
  "slab" is just the export; the physical board is standard).
- Four M3 clearance holes (⌀ 4 mm), 5 mm in from each edge (hole grid
+- Four M3 clearance holes (⌀ 4 mm) at (5.00, 5.04), (40.78, 5.04),
-  35.78 × 78.96 mm).
+  (5.00, 84.00), (40.78, 84.00): hole grid 35.78 × 78.96 mm, centred at
  (22.89, 44.52), slightly off the board centre (23, 44.5).
 - Component placements (pad-group centres from the EasyEDA JSON — these
  are the exact (x, y) the SCAD uses). All in mm from the board's
  bottom-left corner.
@@ -21,7 +21,10 @@ CORNER_R  = 1.0;
 /* [Mounting holes] */
 HOLE_DIA   = 4.0;   // M3 clearance
-HOLE_INSET = 5.0;
+// Exact EasyEDA HOLE positions; the right/bottom insets are 5.22/5.04 mm,
 // not 5, so the grid is 35.78 x 78.96 mm (the body's PCB bosses use it).
 HOLES = [[5.00, 5.04], [40.78, 5.04], [5.00, 84.00], [40.78, 84.00]];
 HOLE_GRID_CENTER = [22.89, 44.52];
 /* [Rendering] */
 SHOW_COMPONENTS = true;
@@ -55,9 +58,7 @@ module board_outline_2d() {
 }
 module mounting_holes_2d() {
-    for (x = [HOLE_INSET, BOARD_W - HOLE_INSET],
+    for (h = HOLES) translate(h) circle(d = HOLE_DIA);
         y = [HOLE_INSET, BOARD_H - HOLE_INSET])
        translate([x, y]) circle(d = HOLE_DIA);
 }
 module pcb() {
@@ -0,0 +1,156 @@
 # OpenSCAD body redesign: notes
 `body.scad` rebuilds the body of `../fusion360/body-bottom/bottom v59.f3d`
 (top + bottom plate, PCB, coxa servos; legs are placeholders).
 ## Source of truth
 The `top` and `bottom` **solids** in `bottom v59.stp` (inside
 `bottom v59.f3d_files.zip`). The `top.dxf` / `bottom.dxf` sketches in the
 same zip are older and differ (front/back notch, side curve, one servo
 pocket with an extra notch), so they are not used.
 Coordinates: the plates are written in the original's top-view frame
 (u, v) = (Fusion x, -Fusion z); `fusion_to_robot()` rotates that by -90°
 into the robot frame of `robot/Config.h` (X = v forward, Y = -u left).
 Fusion's up axis is Y; Fusion Y = 0 is the top face of the bottom plate,
 which is also Z = 0 here.
 `body.scad` slices were overlaid on the original solid edges at every
 feature height (plate faces, standoff split, counterbore floor, nut wells,
 PCB bosses, pivot bosses, battery bay): all match, apart from the fixes
 below.
 ## What the original body is
 - Two 3 mm plates, cavity 27 mm (Z 0..27, top plate Z 27..30).
 - Outline: arm ends r 19.5 around each coxa axis, concave fillets r 15.5
  at the mid arms, quadratic curves at the sides and a notch front/back.
  Fully symmetric (the "asymmetry" seen earlier came from a stray line
  near (128, 8) in `bottom.dxf` and construction points at x = 100).
 - Coxa axes (u, v): corners (±50, ±100), mid (±65, 0) = robot
  (±100, ±50) and (0, ±65), same as `Config.h`.
 - Coxa servos (HS-485HB): ears rest on the top plate (Z 30), case hangs
  in a 41 × 21 pocket down to Z 2. Shaft 10 mm from the outer case end.
  Ear screw holes ⌀2.5, 48.25 × 10 mm. Corner servos turned 50°.
 - Under each coxa axis a ⌀14 × 2 mm pivot boss on the bottom plate; the
  coxa bracket (`hinge1` above / `hinge2` below, leg parts) wraps the
  plate edge between the servo horn and this boss.
 - 4 standoffs ⌀15 at (u, v) (±35, ±30), split at Z 13.5: M3 from the top
  in a ⌀7 counterbore (floor Z 17.5), 8 mm grip, M3 nut in a hex well
  from below (top of the well Z 9.5).
 - PCB: long axis along the body, 4 bosses ⌀5 × 1 mm under the top plate
  on the PCB hole grid (35.78 × 78.96), ⌀2.5 holes (self-tapping M3?),
  ⌀5 × 1 mm recess on top. PCB top face at Z 26.
 - Teensy cut-out 23.78 × 66.96, centred.
 - Slide switch at the front: slot 8 × 16 (v 57..73), ⌀2 screw holes 19 mm
  apart, "ON"/"OFF" engraved 1 mm, readable from behind the robot.
 - Battery bay on the bottom plate: rails 3 × 13.5 mm high at |u| 26.06..29.06
  (52.1 mm between them), from v -74.21 (open, rear) to 31.79, end stop at
  v 28.79..31.79.
 ## Bugs in the original, fixed here
 - Left-front pivot boss at u = -50.894 instead of -50.
 - Right-front corner has no coxa servo (only 5 of 6 placed).
 - Only 2 of 6 legs (the mid legs), plus mirror-naming leftovers and the
  empty `dontdeleteme` component (nothing to port).
 - Hex nut wells rotated randomly; now one orientation.
 ## Leg dimensions (for robot/Config.h and the Unity sim)
 Measured on the original solids (left mid leg, `bottom-leg v31`):
 | Item | Value | Config.h today |
 |------|-------|----------------|
 | Coxa: coxa axis to femur axis, horizontal | 55.0 mm | `COXA_LEN_MM` 55 (matches) |
 | Femur: femur axis to knee axis | 100.0 mm | `FEMUR_LEN_MM` 100 (matches) |
 | Tibia: knee axis to foot ball centre | 150.0 mm | `TIBIA_LEN_MM` 150 (matches) |
 | Foot ball radius | 5.0 mm + 0.5 mm TPU sock wall (same on the real robot) | not modelled |
 | Femur/knee axes height | in the coxa's joint plane, 13.5 mm above the bottom plate's top face | coxa pivot at Z 0 (matches if Z 0 = that plane) |
 | Leg mounts (coxa axes) | (±100, ±50), (0, ±65) | matches |
 | Original pose | femur 0°, tibia -90° (foot straight under the knee) | |
 So the link lengths need no change. What the firmware and Unity don't know
 yet: the ground contact is the foot ball's surface (5 mm + sock from the
 point the IK places), and the body's underside (coxa bracket lower arm) is
 21.5 mm below the joint plane.
 ## Physical limits
 Collision sweep of the model's real parts (2D, per joint, in 0.25° steps;
 cross-checked with full CGAL intersections of body and legs). Joint
 convention as `robot/Config.h`.
 | Joint | Range | Stopped by |
 |-------|-------|-----------|
 | Coxa, mid legs 1/4 | -66.5° .. 66.5° | coxa bracket shell hits the plate waist |
 | Coxa, legs 0 (front-right) / 3 (rear-left) | -95.75° .. 66.75° (sideways mount: -35.75 .. 126.75) | same |
 | Coxa, legs 2 (rear-right) / 5 (front-left) | -66.75° .. 95.75° (sideways mount: -126.75 .. 35.75) | same |
 | Femur | -101.25° .. 101.25° | femur link hits the coxa bracket |
 | Tibia | -177° .. 12.75° | rod folds into the femur link / tibia shell hits it |
 | Servo travel | coxa/femur ±90°, tibia -180..0° | from the `SERVOS` pulse ranges |
 | Leg width at the joints | 33.7 mm to the horn side + 21.5 mm to the bearing side | neighbours touch at 55.2 mm |
 Hexagon layout (owner's request): corner legs mounted 60° round from the mid
 legs (mount angles ±30 / ±90 / ±150); this needs the four corner coxa
 brackets turned 60° on their servo splines. In the firmware (`Config.h`):
 per-leg `COXA_MIN_DEG`/`COXA_MAX_DEG`, all ±60 now (the sideways layout
 needed -32..60 / -60..32 at the corners),
 femur ±80 and tibia -150..-20 unchanged (inside the physical range), and
 `LEG_CLEARANCE_MM` 56 (was 30). `sim_smoke` passes; turning on the spot
 runs at ~77°/s with legs at least 97 mm apart (sideways layout: ~29°/s).
 ## Unity simulation
 `export_unity.py` renders the parts into
 `Hexapod_Simulation_Unity/Assets/HexapodSim/Resources/OpenScadModel/*.bytes`
 (rerun it after changing the SCAD files). `OpenScadModel.cs` hides the old
 scene's robot and builds a new rig with the same names at the exact
 Config.h geometry; `HexapodSimulation.useOpenScadModel` switches it off.
 `Editor/OpenScadModelSnapshot.cs` renders it in batch mode for checks.
 ## Remote (`remote.scad`)
 Rebuilt from `../fusion360/remote/remote v40.f3d` the same way (slices
 match the original). Bugs fixed: the lid was off by (0.406, 0.21, -0.365)
 mm (sat in the ledge, posts overlapping the bosses); the display bezel's
 mesh facets became a clean window; the stray Body12 (an ON-OFF bracket
 line never cut in) is left out. The display is a Nextion NX4832T035
 (3.5" Basic); its board's M3 holes are the lid's 94.2 x 48.5 post grid.
 Reference parts in `remote.scad`: the joysticks are JH-D400X-R4 (4-axis,
 X/Y ±25°, twist ±45°, button; owner), mounted with the dust cover on the
 lid's top face; their M2.5 square is 32.5 mm, so the lid's screw holes moved
 from the original's 33 mm square to 32.5. The battery is an 18650 UPS/boost
 board (89 x 22 mm, SMD-holder version, 22.4 mm tall; owner), on the bottom's
 two d5 standoffs at (±27.9, -15) with the floor slots beside them for a
 strap; its hole spacing (55.8 mm here) is not confirmed. No collisions.
 Also from the owner: the bump on top of the middle post is a lanyard loop
 (the original's tunnel through it is modelled); the square hole is the on/off
 slide switch, mounted on top (same switch as the robot). Inside: an IMU on the
 21 x 9 mm block (assumed GY-521), a USB-C breakout on the side-port block, and
 a Teensy **4.0** (confirmed by the owner, although `platformio.ini` builds
 the remote for a 4.1); it has no mounting holes and is placed on the
 hole-less 8 x 24 mm block as a guess.
 Open: what the 6 mm x 10 mm holes in the bottom bosses hold (magnets?), and
 whether the upper two bosses are meant to be asymmetric (x -80.387 / +82.73).
 ## Notes for future designs
 - Servo wires barely fit on the real robot: the six servo headers hang
  above the battery bay, and the front pair sits right over the bay's end
  stop (X 28.8..31.8, top at Z 13.5). Kept as-is for now; give the plugs and
  wires more room next time (e.g. a lower or shorter end stop, or a battery
  that leaves space under the headers).
 - The nRF24 under the switch is fine on the real robot.
 ## Open questions
 1. Front = switch end (inferred from the ON/OFF text orientation)?
 2. PCB direction: `PCB_USB_FRONT` (Teensy USB, 7805 and LED at the front,
   nRF24 and battery JST at the rear) or reversed?
 3. Battery size. The six servo headers hang above the bay (|Y| 14-15 mm)
   and the JP1/JP4 or JP3/JP6 pair touches the end stop; servo plugs and
   the battery need to share that space.
 4. Leg geometry: in the original the femur servo sits further out than
   `COXA_LEN_MM` = 55 suggests. Check when porting the legs.
@@ -0,0 +1,205 @@
 // 2026 hexapod body: top + bottom plate, rebuilt from the Fusion 360 model
 // fusion360/body-bottom/bottom v59.f3d (the `top` and `bottom` solids in
 // "bottom v59.stp", which are newer than the top.dxf/bottom.dxf sketches).
 //
 // Plate geometry is written in the original's top-view coordinates
 // (u, v) = (Fusion x, -Fusion z), so every number can be checked against
 // the Fusion file. fusion_to_robot() turns that into the robot frame of
 // robot/Config.h (+X forward, +Y left, +Z up): X = v, Y = -u.
 // Z = 0 is the top face of the bottom plate.
 //
 // Deviations from the original (its bugs):
 // - Left-front pivot boss at u = -50 instead of -50.894.
 // - All six coxa servos present (the original has none at right front).
 // - Hex nut wells share one orientation (the original's are rotated randomly).
 use <../main-pcb-2026-11-13/main-pcb.scad>
 include <servo.scad>
 /* [Plates] */
 PLATE_T  = 3.0;    // original: 3 mm, both plates
 CAVITY_H = 27.0;   // inner gap; sized so the servo case ends 2 mm above the bottom plate
 /* [Standoffs: split halfway, screw from the top into a captive nut] */
 STANDOFF_D      = 15.0;
 SCREW_D         = 3.1;
 SCREW_GRIP      = 4.0;   // solid length of each half next to the split
 COUNTERBORE_D   = 7.0;
 NUT_AF          = 5.5;   // M3 nut across flats
 STANDOFFS_UV    = [[35, 30], [-35, 30], [35, -30], [-35, -30]];
 /* [Coxa servos] */
 // Shaft axis per leg, in (u, v), with the direction the case extends from the shaft.
 // Indices match robot/Config.h legs 0..5.
 COXA_UV = [
    [ 50,  100, 230],  // 0 right front
    [ 65,    0, 180],  // 1 right mid
    [ 50, -100, 130],  // 2 right rear
    [-50, -100,  50],  // 3 left rear
    [-65,    0,   0],  // 4 left mid
    [-50,  100, -50],  // 5 left front (original boss at u = -50.894)
 ];
 ARM_R        = 19.5;   // rounded arm end, centred on the coxa axis
 PIVOT_BOSS_D = 14.0;   // under the bottom plate, carries the coxa bracket
 PIVOT_BOSS_H = 2.0;
 /* [Teensy, PCB and switch] */
 TEENSY_CUT    = [23.78, 66.96];   // (u, v) size, centred
 PCB_BOSSES_UV = [[17.89, 39.48], [-17.89, 39.48], [17.89, -39.48], [-17.89, -39.48]];
 PCB_BOSS_D    = 5.0;
 PCB_BOSS_H    = 1.0;              // PCB top face ends up 1 mm under the top plate
 PCB_SCREW_D   = 2.5;
 SWITCH_SLOT   = [[-4, 57], [4, 73]];
 SWITCH_HOLES  = [[0, 55.5], [0, 74.5]];
 SWITCH_HOLE_D = 2.0;
 ENGRAVE_D     = 1.0;
 /* [Battery bay on the bottom plate] */
 BAY_RAIL_U   = [26.06, 29.06];   // inner/outer face of each rail, mirrored in u
 BAY_V        = [-74.21, 31.79];  // open end at -v (rear), closed end at +v
 BAY_STOP     = [[-16, 28.79], [16, 31.79]];
 BAY_H        = 13.5;
 /* [Rendering] */
 SHOW_TOP     = true;
 SHOW_BOTTOM  = true;
 SHOW_PCB     = true;
 SHOW_SERVOS  = true;
 EXPLODE      = 0;      // mm; lifts the top half
 PCB_USB_FRONT = false; // owner: Teensy USB faces away from the switch (rear)
 /* [Hidden] */
 $fa = 2; $fs = 0.3;
 STANDOFF_SPLIT = CAVITY_H / 2;
 TOP_Z = CAVITY_H + PLATE_T;
 module fusion_to_robot() rotate([0, 0, -90]) children();
 // linear_extrude with a convexity, so the preview shows holes correctly.
 module lx(h) linear_extrude(h, convexity = 10) children();
 // ---------- outline -------------------------------------------------------
 function bez2(p, t) = (1-t)*(1-t)*p[0] + 2*(1-t)*t*p[1] + t*t*p[2];
 function rev(l) = [for (i = [len(l)-1:-1:0]) l[i]];
 NOTCH = [[-34.12, 111.31], [0, 71.93], [34.12, 111.31]];   // front/back notch
 WAIST = [[60.03, 83.28], [49.86, 74.48], [50.13, 64.77]];  // corner arm -> side
 FILLET_C = [65, 35];
 FILLET_R = 15.5;
 N = 24;
 // Right half, front to back; the arm circles fill in the chords at the arm ends.
 Q1 = concat(
    [for (i = [N/2:N]) bez2(NOTCH, i/N)],
    [for (i = [0:N]) bez2(WAIST, i/N)],
    [[49.5, 35]],
    [for (a = [180:5:270]) FILLET_C + FILLET_R * [cos(a), sin(a)]],
    [[65, 0]]);
 RIGHT = concat(Q1, [for (p = rev(Q1)) [p[0], -p[1]]]);
 OUTLINE = concat(RIGHT, [for (p = rev(RIGHT)) [-p[0], p[1]]]);
 module outline_2d() {
    polygon(OUTLINE);
    for (c = COXA_UV) translate([c[0], c[1]]) circle(r = ARM_R);
 }
 module at_coxa(c) translate([c[0], c[1]]) rotate([0, 0, c[2]]) children();
 // ---------- top plate -----------------------------------------------------
 module top_plate_2d() {
    difference() {
        outline_2d();
        for (c = COXA_UV) at_coxa(c) servo_pocket_2d();
        square(TEENSY_CUT, center = true);
        for (s = STANDOFFS_UV) translate(s) circle(d = SCREW_D);
        for (b = PCB_BOSSES_UV) translate(b) circle(d = PCB_SCREW_D);
        translate(SWITCH_SLOT[0]) square(SWITCH_SLOT[1] - SWITCH_SLOT[0]);
        for (h = SWITCH_HOLES) translate(h) circle(d = SWITCH_HOLE_D);
    }
 }
 module switch_text() {
    for (t = [["ON", 49.3], ["OFF", 80.6]])
        translate([0, t[1]])
            text(t[0], size = 5.8, halign = "center", valign = "center",
                 font = "Liberation Sans");
 }
 module top_half() render(convexity = 10) {
    difference() {
        union() {
            translate([0, 0, CAVITY_H]) lx(PLATE_T) top_plate_2d();
            for (s = STANDOFFS_UV) translate([s[0], s[1], STANDOFF_SPLIT])
                cylinder(d = STANDOFF_D, h = CAVITY_H - STANDOFF_SPLIT);
            for (b = PCB_BOSSES_UV) translate([b[0], b[1], CAVITY_H - PCB_BOSS_H])
                cylinder(d = PCB_BOSS_D, h = PCB_BOSS_H);
        }
        for (s = STANDOFFS_UV) translate([s[0], s[1], 0]) {
            translate([0, 0, STANDOFF_SPLIT - 1]) cylinder(d = SCREW_D, h = SCREW_GRIP + 2);
            translate([0, 0, STANDOFF_SPLIT + SCREW_GRIP]) cylinder(d = COUNTERBORE_D, h = TOP_Z);
        }
        for (b = PCB_BOSSES_UV) translate([b[0], b[1], 0]) {
            translate([0, 0, CAVITY_H - PCB_BOSS_H - 1]) cylinder(d = PCB_SCREW_D, h = PLATE_T + 2);
            translate([0, 0, TOP_Z - 1]) cylinder(d = PCB_BOSS_D, h = 2);
        }
        translate([0, 0, TOP_Z - ENGRAVE_D]) lx(ENGRAVE_D + 1) switch_text();
    }
 }
 // ---------- bottom plate --------------------------------------------------
 module bay_2d() {
    for (m = [1, -1]) scale([m, 1])
        translate([BAY_RAIL_U[0], BAY_V[0]])
            square([BAY_RAIL_U[1] - BAY_RAIL_U[0], BAY_V[1] - BAY_V[0]]);
    translate(BAY_STOP[0]) square(BAY_STOP[1] - BAY_STOP[0]);
 }
 module bottom_half() render(convexity = 10) {
    difference() {
        union() {
            translate([0, 0, -PLATE_T]) lx(PLATE_T) outline_2d();
            for (s = STANDOFFS_UV) translate([s[0], s[1], 0])
                cylinder(d = STANDOFF_D, h = STANDOFF_SPLIT);
            lx(BAY_H) bay_2d();
            for (c = COXA_UV) translate([c[0], c[1], -PLATE_T - PIVOT_BOSS_H])
                cylinder(d = PIVOT_BOSS_D, h = PIVOT_BOSS_H);
        }
        for (s = STANDOFFS_UV) translate([s[0], s[1], 0]) {
            translate([0, 0, STANDOFF_SPLIT - SCREW_GRIP - 1]) cylinder(d = SCREW_D, h = SCREW_GRIP + 2);
            translate([0, 0, -PLATE_T - 1])
                cylinder(d = NUT_AF / cos(30), h = STANDOFF_SPLIT - SCREW_GRIP + PLATE_T + 1, $fn = 6);
        }
    }
 }
 // ---------- PCB -----------------------------------------------------------
 // Long axis along the body (robot X), holes on the PCB bosses, top face
 // 1 mm under the top plate, Teensy up through the cut-out.
 PCB_T = 1.6;
 PCB_HOLE_CENTER = [22.89, 44.52];   // HOLE_GRID_CENTER in main-pcb.scad
 module pcb_in_body() {
    translate([0, 0, CAVITY_H - PCB_BOSS_H - PCB_T])
        rotate([0, 0, PCB_USB_FRONT ? -90 : 90])
            translate([-PCB_HOLE_CENTER[0], -PCB_HOLE_CENTER[1], 0])
                main_pcb();
 }
 // ---------- assembly ------------------------------------------------------
 module body_servos_uv() for (c = COXA_UV) translate([0, 0, TOP_Z]) at_coxa(c) hs485hb();
 module body_assembly() {
    fusion_to_robot() {
        if (SHOW_BOTTOM) color("#3a3a3a") bottom_half();
        if (SHOW_TOP) translate([0, 0, EXPLODE]) color("#555555") top_half();
        if (SHOW_SERVOS) translate([0, 0, EXPLODE]) body_servos_uv();
    }
    if (SHOW_PCB) translate([0, 0, EXPLODE]) pcb_in_body();
 }
 body_assembly();
@@ -0,0 +1,109 @@
 """Export the OpenSCAD robot as meshes for the Unity simulation.
    python export_unity.py            (from hardware/openscad, needs OpenSCAD)
 Writes Hexapod_Simulation_Unity/Assets/HexapodSim/Resources/OpenScadModel/*.bytes,
 loaded by Assets/HexapodSim/OpenScadModel.cs. Every file is one rig segment
 in the robot frame (mm, +X forward, +Y left, +Z up), relative to the
 segment's pivot, in the rest pose that matches the rig's zero rotations
 (coxa 0, femur 0, tibia -90):
  body           Z = 0 on the joint plane (13.5 mm above the bottom plate)
  leg_<side>_*   left = as leg 4 (mount +90), right = its mirror (mount -90)
 File format (little endian): b"HXM1", int32 groups, then per group
 float32 r, g, b, a, int32 triangles, triangles * 9 float32 (x, y, z).
 Triangles wind counter-clockwise seen from outside (right-handed).
 """
 import os, re, struct, subprocess, sys, tempfile
 HERE = os.path.dirname(os.path.abspath(__file__)).replace("\\", "/")
 OUT = os.path.normpath(os.path.join(HERE, "..", "..", "Hexapod_Simulation_Unity", "Assets",
                                    "HexapodSim", "Resources", "OpenScadModel"))
 OPENSCAD = os.environ.get("OPENSCAD", r"C:/Program Files/OpenSCAD/openscad.exe")
 HEADER = f"use <{HERE}/body.scad>\nuse <{HERE}/leg.scad>\n"
 JOINT_PLANE_Z = 13.5
 def hexcol(h, a=1.0):
    h = h.lstrip("#")
    return [int(h[i:i + 2], 16) / 255 for i in (0, 2, 4)] + [a]
 # segment -> list of (colour, OpenSCAD geometry in the segment's frame)
 BODY = [
    ("#3a3a3a", f"translate([0, 0, -{JOINT_PLANE_Z}]) fusion_to_robot() bottom_half();"),
    ("#555555", f"translate([0, 0, -{JOINT_PLANE_Z}]) fusion_to_robot() top_half();"),
    ("#2a2a2a", f"translate([0, 0, -{JOINT_PLANE_Z}]) fusion_to_robot() body_servos_uv();"),
    ("#2b6b3a", f"translate([0, 0, -{JOINT_PLANE_Z}]) pcb_in_body();"),
 ]
 LEFT = "rotate([0, 0, 90]) "   # leg frame -> robot frame for the left legs (mount +90)
 LEG = {
    "coxa": [
        ("#d9822b", LEFT + "{ coxa_bracket_upper(); coxa_bracket_lower(); }"),
        ("#bdbdbd", LEFT + "translate([55, 0, 0]) along_y(28.7) horn_adapter();"),
        ("#5a3a1e", LEFT + "coxa_cables();"),
    ],
    "femur": [
        ("#4a7fbf", LEFT + "{ link_channel(); link_lid(); }"),
        ("#2a2a2a", LEFT + "link_servos();"),
        ("#5a3a1e", LEFT + "femur_cables();"),
    ],
    "tibia": [
        ("#5fa35f", LEFT + "{ tibia_bearing_half(); tibia_horn_half(); }"),
        ("#bdbdbd", LEFT + "along_y(28.7) horn_adapter();"),
        ("#1c1c1c", LEFT + "foot_sock();"),
    ],
 }
 def render(geometry, tmp):
    scad = os.path.join(tmp, "part.scad"); stl = os.path.join(tmp, "part.stl")
    with open(scad, "w") as f:
        f.write(HEADER + geometry + "\n")
    r = subprocess.run([OPENSCAD, "-o", stl, scad], capture_output=True, text=True)
    if r.returncode != 0 or not os.path.exists(stl):
        sys.exit(f"OpenSCAD failed on: {geometry}\n{r.stderr}")
    tris = []
    num = r"([-+0-9.eE]+)"
    for m in re.finditer(r"outer loop\s+vertex\s+%s\s+%s\s+%s\s+vertex\s+%s\s+%s\s+%s\s+vertex\s+%s\s+%s\s+%s" % ((num,) * 9),
                         open(stl).read()):
        tris.append([float(v) for v in m.groups()])
    os.remove(stl)
    return tris
 def mirror_y(tris):
    # (x, y, z) -> (x, -y, z) and swap two vertices to keep outward winding
    out = []
    for t in tris:
        a, b, c = t[0:3], t[3:6], t[6:9]
        a, b, c = [a[0], -a[1], a[2]], [b[0], -b[1], b[2]], [c[0], -c[1], c[2]]
        out.append(a + c + b)
    return out
 def write(name, groups):
    path = os.path.join(OUT, name + ".bytes")
    with open(path, "wb") as f:
        f.write(b"HXM1" + struct.pack("<i", len(groups)))
        for col, tris in groups:
            f.write(struct.pack("<4f", *col) + struct.pack("<i", len(tris)))
            for t in tris:
                f.write(struct.pack("<9f", *t))
    print(f"  {name}: {sum(len(t) for _, t in groups)} triangles")
 def main():
    os.makedirs(OUT, exist_ok=True)
    with tempfile.TemporaryDirectory() as tmp:
        print("body")
        write("body", [(hexcol(c), render(g, tmp)) for c, g in BODY])
        for seg, parts in LEG.items():
            print("leg", seg)
            groups = [(hexcol(c), render(g, tmp)) for c, g in parts]
            write(f"leg_left_{seg}", groups)
            write(f"leg_right_{seg}", [(c, mirror_y(t)) for c, t in groups])
 if __name__ == "__main__":
    main()
@@ -0,0 +1,383 @@
 // 2026 hexapod leg, rebuilt from the Fusion 360 model
 // fusion360/body-bottom/bottom v59.f3d (bottom-leg v31 + hinge1/hinge2).
 //
 // Leg frame (left leg): origin on the coxa axis at the joint plane
 // (13.5 mm above the bottom plate's top face), +x outward along the leg,
 // +y along the femur/knee axes towards the horn side (the robot's rear),
 // +z up. Right legs are the mirror image (see robot.scad).
 // leg(pose) poses it with the firmware's joint convention (robot/Config.h):
 // coxa + = CCW seen from above, femur + = up, tibia relative to the femur,
 // + = up. The original is modelled at [0, 0, -90].
 //
 // Every joint uses the same layout: servo ears 16.5 mm from the joint
 // plane; a 5 mm horn plate at 28.7..33.7 on one side holding a printed
 // horn adapter; a 3 mm bearing plate at -21.5..-18.5 on the other side,
 // whose ring takes a 14 mm boss on the opposite part; plates shaped as a
 // lens (r 25.5 around the axis, cut by r 19.963 offset 9.463 towards the
 // part's body); and a wrap shell up to r 25.5 for clearance.
 //
 // Deviations from the original (its bugs):
 // - Tibia halves split exactly at y = 0 (one half was 0.1 mm off, holes up
 //   to 0.03 mm apart, different blade spline nets).
 // - Lid locating lips all 0.8 mm (the original's were 0.5..0.9 mm).
 // - The foot sock sits on the foot (the original's was 10/13.5 mm off).
 include <servo.scad>
 /* [Links (match robot/Config.h)] */
 COXA_LEN  = 55;
 FEMUR_LEN = 100;
 TIBIA_LEN = 150;   // knee axis to foot ball centre
 /* [Shared joint design] */
 SHELL_R          = 25.5;
 BRACKET_SHELL_IN = 23.5;
 TIBIA_SHELL_IN   = 24.0;
 LENS_R           = 19.963;
 LENS_OFFSET      = 9.463;
 HORN_PLATE       = [28.7, 33.7];
 BEARING_PLATE    = [-21.5, -18.5];
 RING             = [7.2, 10.5, 1.5];   // pocket radius, outer radius, height
 BOSS_D           = 14;
 BOSS_H           = 2;
 SERVO_EAR_PLANE  = 16.5;
 HORN_SQUARE      = 30;
 JOIN             = 1;      // shells reach this far into their plates, so parts fuse
 HORN_HUB_D       = 9.2;
 HORN_CROSS_DEPTH = 2;
 /* [Fasteners] */
 M3_D      = 3.1;
 M3_HEAD_D = 5.7;
 M3_NUT_AF = 5.7;
 /* [Coxa bracket] */
 BLOCK_Z        = [-12, 12.5];
 BLOCK_Y        = 15;
 BRACKET_BOLTS  = [[26.4, 10.92], [26.4, -10.92]];   // (x, y), vertical
 CABLE_D        = 6;
 /* [Femur link] */
 LINK_X     = [-19, 119];
 LINK_Z     = 13;      // half height
 LINK_R     = 3;
 LINK_WALL  = 2;
 LINK_TOP   = [13.5, 16.5];   // top wall, carries both servos
 LINK_LID   = [-16.5, -13.5];
 LIP        = [0.8, 3, 0.5];  // thickness, height, clearance to the wall
 CABLE_SLOT = [-12.5, 3];     // slot for x < -12.5, |y| < 3
 /* [Tibia] */
 LOBE_X       = 25.5;
 LOBE_R       = 14.985;
 LOBE_Y       = 12;
 TIBIA_BOLTS  = [[26.43, 10.585], [26.43, -10.585]];  // (x, z), along y
 ROD_R        = 5;
 ROD_PATH     = [[28.5, -0], [47.41, -36.13], [0, -TIBIA_LEN]];  // (x, z), quadratic Bezier
 /* [Foot sock (TPU)] */
 SOCK_T   = 0.5;    // wall, same as the real printed socks
 SOCK_LEN = 12.2;   // along the rod from the foot ball centre
 /* [Rendering] */
 SHOW_SERVOS   = true;
 SHOW_ADAPTERS = true;
 SHOW_SOCK     = true;
 SHOW_CABLES   = true;
 /* [Hidden] */
 $fa = 2; $fs = 0.3;
 C_BRACKET = "#d9822b";
 C_LINK    = "#4a7fbf";
 C_TIBIA   = "#5fa35f";
 C_ADAPTER = "#bdbdbd";
 C_SOCK    = "#1c1c1c";
 BIG = 200;
 // ---------- helpers -------------------------------------------------------
 function rot2(p, a) = [p[0]*cos(a) - p[1]*sin(a), p[0]*sin(a) + p[1]*cos(a)];
 function bez(p, t) = (1-t)*(1-t)*p[0] + 2*(1-t)*t*p[1] + t*t*p[2];
 // Shell around the local Z axis between r_in and SHELL_R, ±45° about angle a.
 module shell(r_in, z0, z1, a = 0)
    translate([0, 0, z0]) rotate([0, 0, a - 45])
        lx(z1 - z0) intersection() {
            difference() { circle(r = SHELL_R); circle(r = r_in); }
            polygon([[0, 0], [2 * SHELL_R, 0], [2 * SHELL_R, 2 * SHELL_R], [0, 2 * SHELL_R]]);
        }
 // linear_extrude with a convexity, so the preview shows holes and shells.
 module lx(h) linear_extrude(h, convexity = 10) children();
 // Plate outline around an axis at the origin, biased by `off` along x.
 module lens_2d(off) intersection() {
    circle(r = SHELL_R);
    translate([off, 0]) circle(r = LENS_R);
 }
 // Turns a part built along local Z into one along +y (for horizontal axes).
 module along_y(y0) translate([0, y0, 0]) rotate([-90, 0, 0]) children();
 module ring(z0) translate([0, 0, z0]) difference() {
    cylinder(r = RING[1], h = RING[2]);
    translate([0, 0, -1]) cylinder(r = RING[0], h = RING[2] + 2);
 }
 module hex_well(af, h) cylinder(d = af / cos(30), h = h, $fn = 6);
 // The servo cross horn, arms on the diagonals (same in every horn pocket).
 CROSS_ARM = concat([[6.106, 0], [10.926, 6.853]],
                   [for (a = [-34.56 : 10 : 125.44]) [8.874, 8.874] + 2.88 * [cos(a), sin(a)]],
                   [[6.853, 10.926]]);
 module cross_2d() polygon([for (k = [0:3]) for (p = CROSS_ARM) rot2(p, 90 * k)]);
 // Hub hole through, cross pocket in the top HORN_CROSS_DEPTH of a 5 mm plate.
 module horn_cut(h = 5) {
    translate([0, 0, -1]) cylinder(d = HORN_HUB_D, h = h + 2);
    translate([0, 0, h - HORN_CROSS_DEPTH]) lx(HORN_CROSS_DEPTH + 1) cross_2d();
 }
 // Printed horn adapter ("servo horn v6"): sits in a horn plate's square window.
 module horn_adapter() color(C_ADAPTER) render(convexity = 10) difference() {
    translate([-HORN_SQUARE/2, -HORN_SQUARE/2, 0]) cube([HORN_SQUARE, HORN_SQUARE, 5]);
    horn_cut();
 }
 // ---------- coxa bracket --------------------------------------------------
 // Two printed halves split at the joint plane, bolted with 2 x M3.
 // Fills the gap between the two shells; reaches 1 mm into both shell walls so
 // each bracket half prints as one solid (in the original they are separate bodies).
 module bracket_block(z0, z1) difference() {
    translate([18, -BLOCK_Y, z0]) cube([20, 2 * BLOCK_Y, z1 - z0]);
    cylinder(r = SHELL_R - 1, h = BIG, center = true);
    translate([COXA_LEN, 0, 0]) rotate([90, 0, 0]) cylinder(r = SHELL_R - 1, h = BIG, center = true);
 }
 module bracket_common_cuts() {
    translate([20, 0, 0]) rotate([0, 90, 0]) cylinder(d = CABLE_D, h = 15);
    for (b = BRACKET_BOLTS) translate([b[0], b[1], -5]) cylinder(d = M3_D, h = 10);
 }
 module coxa_bracket_upper() color(C_BRACKET) render(convexity = 10) difference() {
    union() {
        shell(BRACKET_SHELL_IN, 0, HORN_PLATE[0] + JOIN);
        translate([0, 0, HORN_PLATE[0]]) difference() {
            lx(HORN_PLATE[1] - HORN_PLATE[0]) intersection() {
                circle(r = SHELL_R);
                union() {
                    square(HORN_SQUARE, center = true);
                    translate([LENS_OFFSET, 0]) circle(r = LENS_R);
                }
            }
            horn_cut();
        }
        bracket_block(0, BLOCK_Z[1]);
        translate([COXA_LEN, 0, 0]) {
            along_y(0) shell(BRACKET_SHELL_IN, 0, HORN_PLATE[0] + JOIN, 180);
            along_y(HORN_PLATE[0]) lx(HORN_PLATE[1] - HORN_PLATE[0]) difference() {
                lens_2d(-LENS_OFFSET);
                square(HORN_SQUARE, center = true);
            }
        }
    }
    bracket_common_cuts();
    for (b = BRACKET_BOLTS) translate([b[0], b[1], 4]) cylinder(d = M3_HEAD_D, h = 10);
 }
 module coxa_bracket_lower() color(C_BRACKET) render(convexity = 10) difference() {
    union() {
        shell(BRACKET_SHELL_IN, BEARING_PLATE[1] - JOIN, 0);
        translate([0, 0, BEARING_PLATE[0]])
            lx(BEARING_PLATE[1] - BEARING_PLATE[0]) lens_2d(LENS_OFFSET);
        ring(BEARING_PLATE[1]);
        bracket_block(BLOCK_Z[0], 0);
        translate([COXA_LEN, 0, 0]) {
            along_y(BEARING_PLATE[1] - JOIN) shell(BRACKET_SHELL_IN, 0, -BEARING_PLATE[1] + JOIN, 180);
            along_y(BEARING_PLATE[0]) lx(BEARING_PLATE[1] - BEARING_PLATE[0])
                lens_2d(-LENS_OFFSET);
            along_y(BEARING_PLATE[1]) ring(0);
        }
    }
    bracket_common_cuts();
    for (b = BRACKET_BOLTS) translate([b[0], b[1], BLOCK_Z[0] - 1]) hex_well(M3_NUT_AF, 9);
 }
 // ---------- femur link ----------------------------------------------------
 // Femur frame: origin on the femur axis, knee at x = FEMUR_LEN.
 module link_profile_2d(inset = 0, r = LINK_R)
    translate([LINK_X[0] + inset, -LINK_Z + inset])
        offset(r = r) offset(delta = -r)
            square([LINK_X[1] - LINK_X[0] - 2*inset, 2*(LINK_Z - inset)]);
 SERVO_SHAFTS = [[0, 0], [FEMUR_LEN, 180]];   // (x, direction the case extends)
 module link_channel() color(C_LINK) render(convexity = 10) difference() {
    along_y(LINK_LID[1]) lx(LINK_TOP[1] - LINK_LID[1]) link_profile_2d();
    along_y(LINK_LID[1] - 1) lx(LINK_TOP[0] - LINK_LID[1] + 1)
        link_profile_2d(LINK_WALL, 1);
    for (s = SERVO_SHAFTS) along_y(LINK_TOP[0] - 1) translate([s[0], 0]) rotate([0, 0, s[1]])
        lx(LINK_TOP[1] - LINK_TOP[0] + 2) servo_pocket_2d();
    translate([LINK_X[0] - 1, -CABLE_SLOT[1], -BIG/2])
        cube([CABLE_SLOT[0] - LINK_X[0] + 1, 2 * CABLE_SLOT[1], BIG]);
 }
 module link_lid() color(C_LINK) render(convexity = 10) {
    along_y(LINK_LID[0]) lx(LINK_LID[1] - LINK_LID[0]) link_profile_2d();
    for (x = [0, FEMUR_LEN]) translate([x, 0, 0])
        along_y(LINK_LID[0] - BOSS_H) cylinder(d = BOSS_D, h = BOSS_H);
    in = LINK_WALL + LIP[2];
    along_y(LINK_LID[1]) lx(LIP[1]) {
        for (m = [1, -1]) scale([1, m])
            translate([-10, LINK_Z - in - LIP[0]]) square([120, LIP[0]]);
        translate([LINK_X[0] + in, -8]) square([LIP[0], 16]);
        translate([LINK_X[1] - in - LIP[0], -8]) square([LIP[0], 16]);
    }
 }
 module link_servos() if (SHOW_SERVOS)
    for (s = SERVO_SHAFTS) translate([s[0], SERVO_EAR_PLANE, 0])
        rotate([-90, 0, 0]) rotate([0, 0, s[1]]) hs485hb();
 // ---------- tibia ---------------------------------------------------------
 // Knee frame: origin on the knee axis, axes as the femur frame in the
 // original pose (tibia at -90 degrees, rod hanging down).
 ROD_N = 30;
 module rod() for (i = [0:ROD_N-1]) hull() {
    a = bez(ROD_PATH, i / ROD_N); b = bez(ROD_PATH, (i + 1) / ROD_N);
    translate([a[0], 0, a[1]]) sphere(r = ROD_R, $fn = 36);
    translate([b[0], 0, b[1]]) sphere(r = ROD_R, $fn = 36);
 }
 module half_space(side) translate([-BIG, side > 0 ? 0 : -BIG, -BIG]) cube([2*BIG, BIG, 2*BIG]);
 // Bolt lobe behind the knee, only outside the shell (r > SHELL_R), so it
 // clears the femur link's end at any knee angle.
 module tibia_lobe(y0, y1) along_y(y0) lx(y1 - y0) difference() {
    translate([LOBE_X, 0]) circle(r = LOBE_R);
    circle(r = SHELL_R - JOIN);
 }
 // One half of the rod, trimmed to stay outside the shell's inner radius.
 module rod_half(side) difference() {
    intersection() { rod(); half_space(side); }
    along_y(-BIG/2) cylinder(r = TIBIA_SHELL_IN, h = BIG);
 }
 module tibia_bolts(y0, h, d) for (b = TIBIA_BOLTS) translate([b[0], 0, b[1]]) along_y(y0) cylinder(d = d, h = h);
 // Bearing side (original "leg left 1"); M3 heads in its 8 mm counterbores.
 module tibia_bearing_half() color(C_TIBIA) render(convexity = 10) difference() {
    union() {
        along_y(BEARING_PLATE[0]) lx(BEARING_PLATE[1] - BEARING_PLATE[0]) lens_2d(LENS_OFFSET);
        along_y(BEARING_PLATE[1]) ring(0);
        along_y(BEARING_PLATE[1] - JOIN) shell(TIBIA_SHELL_IN, 0, -BEARING_PLATE[1] + JOIN);
        tibia_lobe(-LOBE_Y, 0);
        rod_half(-1);
    }
    tibia_bolts(-4, 5, M3_D);
    tibia_bolts(-LOBE_Y - 1, LOBE_Y - 4 + 1, M3_HEAD_D);
 }
 // Horn side (original "leg left 2"); M3 nuts in its hex wells.
 module tibia_horn_half() color(C_TIBIA) render(convexity = 10) difference() {
    union() {
        along_y(HORN_PLATE[0]) lx(HORN_PLATE[1] - HORN_PLATE[0]) difference() {
            lens_2d(LENS_OFFSET);
            square(HORN_SQUARE, center = true);
        }
        along_y(0) shell(TIBIA_SHELL_IN, 0, HORN_PLATE[0] + JOIN);
        tibia_lobe(0, LOBE_Y);
        rod_half(1);
    }
    tibia_bolts(-1, 5, M3_D);
    for (b = TIBIA_BOLTS) translate([b[0], 0, b[1]]) along_y(4) hex_well(M3_NUT_AF, LOBE_Y);
 }
 // TPU sock over the foot ball and the end of the rod.
 FOOT = [ROD_PATH[2][0], 0, ROD_PATH[2][1]];
 SOCK_DIR = [ROD_PATH[1][0] - ROD_PATH[2][0], 0, ROD_PATH[1][1] - ROD_PATH[2][1]]
           / norm([ROD_PATH[1][0] - ROD_PATH[2][0], ROD_PATH[1][1] - ROD_PATH[2][1]]);
 module foot_sock() color(C_SOCK) render(convexity = 10) difference() {
    intersection() {
        hull() {
            translate(FOOT) sphere(r = ROD_R + SOCK_T);
            translate(FOOT + SOCK_LEN * SOCK_DIR) sphere(r = ROD_R + SOCK_T);
        }
        // flat open end, perpendicular to the rod
        translate(FOOT) rotate([0, atan2(SOCK_DIR[0], SOCK_DIR[2]), 0])
            translate([-BIG/2, -BIG/2, -BIG]) cube([BIG, BIG, BIG + SOCK_LEN]);
    }
    rod();
 }
 // ---------- servo cables (reference only) ---------------------------------
 // Route of the original: along the lid under the servo cases, up through
 // the link's end slot, through the bracket's cable channel, into the body
 // cavity at the arm end (the channel sits at the cavity's mid-height).
 // The lead leaves the case at the end opposite the shaft, low down.
 CABLE_W = 2.4;
 C_CABLE = "#5a3a1e";
 module cable(pts) color(C_CABLE)
    for (i = [0:len(pts)-2]) hull() {
        translate(pts[i]) sphere(d = CABLE_W, $fn = 12);
        translate(pts[i+1]) sphere(d = CABLE_W, $fn = 12);
    }
 // Femur frame part of a lead: case exit -> along the lid -> out of the end slot.
 function link_lead(exit_x, toward, z) = [
    [exit_x, -9, z], [exit_x + toward * 2, -12.3, z], [-12, -12.3, z],
    [-15.5, -8, z * 0.5], [-17, 0, 0], [LINK_X[0] - 4, 0, 0]];
 // Leg frame part, original pose: bracket channel -> into the body cavity.
 LEAD_BODY = [[COXA_LEN - 25.5 - 1, 0, 0], [16, 0, 0], [12, 12, 0], [-35, 12, 0]];
 // Coxa-frame part: bridge from the link's end slot to the bracket channel,
 // then on into the body.
 module coxa_cables() {
    cable(LEAD_BODY);
    cable([[COXA_LEN + LINK_X[0] - 4, 0, 0], [COXA_LEN - 25.5 - 1, 0, 0]]);
 }
 // Femur-frame part: both leads inside the femur link.
 module femur_cables() {
    cable(link_lead(30, 1, -3));            // femur servo
    cable(link_lead(FEMUR_LEN - 30, -1, 3)); // knee servo
 }
 module leg_cables(pose) rotate([0, 0, pose[0]]) {
    coxa_cables();
    translate([COXA_LEN, 0, 0]) rotate([0, -pose[1], 0]) femur_cables();
 }
 // ---------- posed leg -----------------------------------------------------
 module leg(pose = [0, 0, -90]) {
    if (SHOW_CABLES) leg_cables(pose);
    leg_parts(pose);
 }
 module leg_parts(pose) rotate([0, 0, pose[0]]) {
    coxa_bracket_upper();
    coxa_bracket_lower();
    translate([COXA_LEN, 0, 0]) {
        if (SHOW_ADAPTERS) along_y(HORN_PLATE[0]) horn_adapter();
        rotate([0, -pose[1], 0]) {
            link_channel();
            link_lid();
            link_servos();
            translate([FEMUR_LEN, 0, 0]) rotate([0, -(pose[2] + 90), 0]) {
                tibia_bearing_half();
                tibia_horn_half();
                if (SHOW_ADAPTERS) along_y(HORN_PLATE[0]) horn_adapter();
                if (SHOW_SOCK) foot_sock();
            }
        }
    }
 }
 leg();
@@ -0,0 +1,245 @@
 // Handheld remote: bottom shell + lid, rebuilt from the Fusion 360 model
 // fusion360/remote/remote v40.f3d (the `bottom` and `top` solids in
 // "remote v40.stp"; remote v4 is an early flat stick plate).
 //
 // Written in the original's top-view coordinates (u, v) = (Fusion x,
 // -Fusion z), so every number can be checked against the Fusion file.
 // Z = 0 on the rim of the bottom shell (the lid's top face sits flush).
 // Text on the lid reads upright with +v up.
 //
 // Deviations from the original (its bugs):
 // - Lid moved by (-0.406, -0.21, +0.365) mm: it was off-centre and sat
 //   0.365 mm into the bottom's ledge, its posts overlapping the bosses.
 // - The display bezel's stepped facets (an imported mesh) are a clean
 //   rectangular window plus its 0.45 mm lip; small clip notches omitted.
 // - Body12 (an "ON-OFF" bracket line that was never cut into the lid) left out.
 /* [Shell] */
 CORNERS  = [[-66.5, -58.883], [66.5, -58.883], [66.5, 41.117], [-66.5, 41.117]];
 R_OUT    = 37.5;   // outside of the bottom shell
 R_WALL   = 32.5;   // inside of the walls (5 mm)
 R_LEDGE  = 35.5;   // rebate the lid drops into
 R_LID    = 35.0;   // lid outline (0.5 mm clearance in the rebate)
 FLOOR_Z  = [-45, -42];
 LEDGE_Z  = -5;
 LID_Z    = [-5, 0];
 /* [Fixing] */
 BOSSES   = [[-30, 40], [30, 40], [-80.387, -72.711], [82.73, -73]];
 BOSS_D   = 10;
 BOSS_TOP = -35;
 BOSS_HOLE_D = 6;     // through the floor, 10 mm deep (magnets?)
 POST_HOLE_D = 3;     // blind, from the lid post's end
 /* [Sticks, switch, display] */
 STICKS       = [[-66.5, 41.117], [66.5, 41.117]];
 STICK_HOLE_D = 40;
 STICK_SCREW  = 16.25;  // 4 x d2 (M2.5 self-tapping) on the joystick's 32.5 mm square (original: 33)
 SWITCH_SLOT  = [[-4, 33.975], [4, 49.975]];   // on/off slide switch, mounted on top (same as the robot's)
 SWITCH_HOLES = [[0, 32.475], [0, 51.475]];
 PILL         = [[0, 5], [0, 15]];   // centres of the round ends
 WINDOW       = [[-37.94, -66.964], [37.96, -16.064]];
 WINDOW_LIP   = [0.45, -1.05, -0.45];   // inset, z range
 DISPLAY_POCKET = [[-49.0, -73.0], [52.258, -10.0]];
 DISPLAY_POCKET_Z = -2;   // pocket from the lid's underside up to here
 DISPLAY_POSTS = [[-44.939, -65.772], [49.261, -65.772], [-44.939, -17.272], [49.261, -17.272]];
 TEXT = [["ON", [0.7, 26.29]], ["OFF", [0.15, 57.61]]];
 ENGRAVE_D = 1;
 /* [Rendering] */
 SHOW_BOTTOM  = true;
 SHOW_LID     = true;
 SHOW_DISPLAY = true;
 SHOW_STICKS  = true;
 SHOW_BATTERY = true;
 EXPLODE      = 0;
 /* [Hidden] */
 $fa = 2; $fs = 0.3;
 BIG = 300;
 module lx(h) linear_extrude(h, convexity = 10) children();
 module rounded_2d(r) hull() for (c = CORNERS) translate(c) circle(r = r);
 module stadium_2d(a, b, r) hull() { translate(a) circle(r = r); translate(b) circle(r = r); }
 // ---------- bottom shell --------------------------------------------------
 module remote_bottom() render(convexity = 10) difference() {
    union() {
        difference() {
            translate([0, 0, FLOOR_Z[0]]) lx(-FLOOR_Z[0]) rounded_2d(R_OUT);
            translate([0, 0, FLOOR_Z[1]]) lx(BIG) rounded_2d(R_WALL);
            translate([0, 0, LEDGE_Z]) lx(BIG) rounded_2d(R_LEDGE);
        }
        for (b = BOSSES) translate([b[0], b[1], FLOOR_Z[1] - 1]) cylinder(d = BOSS_D, h = BOSS_TOP - FLOOR_Z[1] + 1);
        // blocks rising from the floor
        translate([-10.5, 29, FLOOR_Z[1] - 1]) cube([21, 9, -17 - FLOOR_Z[1] + 1]);
        translate([-4, 44, FLOOR_Z[1] - 1]) cube([8, 24, -17 - FLOOR_Z[1] + 1]);
        for (m = [-1, 1]) translate([m * 27.9, -15, FLOOR_Z[1] - 1]) cylinder(d = 5, h = 4);
        translate([88, -10, FLOOR_Z[1] - 1]) cube([12, 14, -28 - FLOOR_Z[1] + 1]);   // port board block
        // post up through the lid's slot, with a rounded lanyard loop on top
        translate([0, 0, FLOOR_Z[1] - 1]) lx(-FLOOR_Z[1] + 1) stadium_2d(PILL[0], PILL[1], 4.75);
        difference() {
            intersection() {
                hull() for (p = PILL) translate([p[0], p[1], 2.75]) sphere(r = 4.75);
                translate([-10, 0, 0]) cube([20, 30, 10]);
            }
            hull() for (p = PILL) translate([-10, p[1], 2.75]) rotate([0, 90, 0]) cylinder(r = 2.75, h = 20);
        }
    }
    for (b = BOSSES) translate([b[0], b[1], FLOOR_Z[0] - 1]) cylinder(d = BOSS_HOLE_D, h = BOSS_TOP - FLOOR_Z[0] + 2);
    for (m = [-1, 1]) translate([m * 6.562, 35, FLOOR_Z[1]]) cylinder(d = 3, h = 30);
    for (m = [-1, 1]) translate([m * 27.9, -15, FLOOR_Z[1]]) cylinder(d = 3, h = 10);
    for (m = [-1, 1]) translate([0, 0, FLOOR_Z[0] - 1])
        lx(5) stadium_2d([m * 23.9, -17], [m * 23.9, -13], 1);
    translate([98, -10, -35]) cube([10, 14, 15]);   // side port opening
    for (v = [-7.5, 1.5]) translate([91, v, -37]) cylinder(d = 3, h = 10);
 }
 // ---------- lid -----------------------------------------------------------
 module lid_plate_2d() difference() {
    rounded_2d(R_LID);
    for (s = STICKS) translate(s) {
        circle(d = STICK_HOLE_D);
        for (du = [-1, 1], dv = [-1, 1]) translate([du, dv] * STICK_SCREW) circle(d = 2);
    }
    stadium_2d(PILL[0], PILL[1], 5);
    translate(SWITCH_SLOT[0]) square(SWITCH_SLOT[1] - SWITCH_SLOT[0]);
    for (h = SWITCH_HOLES) translate(h) circle(d = 2);
    translate(WINDOW[0]) offset(r = 0.5) offset(delta = -0.5) square(WINDOW[1] - WINDOW[0]);
 }
 module remote_lid() render(convexity = 10) difference() {
    union() {
        translate([0, 0, LID_Z[0]]) lx(LID_Z[1] - LID_Z[0]) lid_plate_2d();
        for (b = BOSSES) translate([b[0], b[1], BOSS_TOP]) cylinder(d = BOSS_D, h = LID_Z[0] - BOSS_TOP + 1);
        // window lip, left over from the original's display bezel
        translate([0, 0, WINDOW_LIP[1]]) lx(WINDOW_LIP[2] - WINDOW_LIP[1]) difference() {
            translate(WINDOW[0]) square(WINDOW[1] - WINDOW[0]);
            translate(WINDOW[0] + [1, 1] * WINDOW_LIP[0]) square(WINDOW[1] - WINDOW[0] - [2, 2] * WINDOW_LIP[0]);
        }
    }
    translate([0, 0, LID_Z[0] - 1]) lx(DISPLAY_POCKET_Z - LID_Z[0] + 1) difference() {
        translate(DISPLAY_POCKET[0]) square(DISPLAY_POCKET[1] - DISPLAY_POCKET[0]);
        for (p = DISPLAY_POSTS) translate(p) circle(d = 6);
    }
    for (p = DISPLAY_POSTS) translate([p[0], p[1], LID_Z[0] - 1]) cylinder(d = 2.5, h = 4);
    for (b = BOSSES) translate([b[0], b[1], BOSS_TOP - 1]) cylinder(d = POST_HOLE_D, h = LID_Z[0] - BOSS_TOP + 1);
    for (t = TEXT) translate([t[1][0], t[1][1], LID_Z[1] - ENGRAVE_D]) lx(ENGRAVE_D + 1)
        text(t[0], size = 5.8, halign = "center", valign = "center", font = "Liberation Sans");
 }
 // ---------- reference parts -----------------------------------------------
 // Nextion NX4832T035 (3.5" Basic): 100.5 x 54.94 mm board, M3 holes 3.15 /
 // 3.22 mm from its edges = the lid's 94.2 x 48.5 post grid; LCD module
 // approximate, its visible area (73.44 x 48.96) under the window.
 module nextion_3_5() {
    centre = (DISPLAY_POSTS[0] + DISPLAY_POSTS[3]) / 2;
    translate([centre[0], centre[1], DISPLAY_POCKET_Z - 4.5 - 1.6]) {
        color("#1e5a2a") difference() {
            translate([-100.5/2, -54.94/2, 0]) cube([100.5, 54.94, 1.6]);
            for (p = DISPLAY_POSTS) translate([p[0] - centre[0], p[1] - centre[1], -1]) cylinder(d = 3.2, h = 4);
        }
    }
    win = (WINDOW[0] + WINDOW[1]) / 2;
    color("#202020") translate([win[0] - 84/2, win[1] - 54/2, DISPLAY_POCKET_Z - 4.5]) cube([84, 54, 4.5]);
    color("#3050a0") translate([win[0] - 73.44/2, win[1] - 48.96/2, DISPLAY_POCKET_Z - 0.2]) cube([73.44, 48.96, 0.2]);
 }
 // JH-D400X-R4 4-axis joystick (X/Y +-25 deg, twist +-45 deg, button),
 // from its dimension drawing. Mounted with its dust cover on the lid's top
 // face; the body hangs through the d40 opening. Local frame: stick axis on
 // Z, Z = 0 on the dust cover's underside. Pots on +X and +Y.
 JOY_COVER_D = 53.5;
 JOY_COVER_T = 3;       // not dimensioned; drawing proportions
 JOY_BOX     = 40.4;    // control box, square
 JOY_BOX_H   = 25.5;
 JOY_BELOW   = 42;      // box bottom to dust cover top
 JOY_ABOVE   = 52.5;    // dust cover top to button top
 JOY_POT_D   = 16.5;
 JOY_POT_L   = (49.6 - 40.4);
 module jh_d400x() {
    top = JOY_COVER_T;
    color("#202020") {
        difference() {
            cylinder(d = JOY_COVER_D, h = JOY_COVER_T);
            for (du = [-1, 1], dv = [-1, 1]) translate([du * 16.25, dv * 16.25, -1]) cylinder(d = 2.7, h = 5);
        }
        translate([0, 0, top]) cylinder(d1 = 39.5, d2 = 30, h = 3);              // dust ring / boot
        translate([0, 0, top - JOY_BELOW]) translate([-JOY_BOX/2, -JOY_BOX/2, 0]) cube([JOY_BOX, JOY_BOX, JOY_BOX_H]);
        translate([0, 0, top - JOY_BELOW + JOY_BOX_H]) cylinder(d = 34, h = JOY_BELOW - JOY_BOX_H - JOY_COVER_T + 0.01);
        for (a = [0, 90]) rotate([0, 0, a])
            translate([JOY_BOX/2, 0, top - JOY_BELOW + JOY_BOX_H/2]) rotate([0, 90, 0]) cylinder(d = JOY_POT_D, h = JOY_POT_L);
        // handle: neck, knurled body, top with the button
        translate([0, 0, top + 6]) cylinder(d = 6, h = 12);
        translate([0, 0, top + 16]) cylinder(d = 22, h = 8);
        translate([0, 0, top + 24]) cylinder(d = 35, h = 22);
        translate([0, 0, top + 46]) cylinder(d1 = 35, d2 = 26, h = 5);
    }
    color("#c0c0c0") translate([0, 0, top + 51]) cylinder(d = 8, h = JOY_ABOVE - 51);
 }
 // 18650 UPS / boost board (5/9/12 V, Type-C charging), "SMD battery box"
 // version: 89 x 22 mm board, holder on top, 22.4 mm overall, d3 holes.
 // Placed on the bottom's two d5 standoffs at (+-27.9, -15); the board's real
 // hole spacing isn't confirmed. The floor slots beside them take a strap.
 UPS_CENTRE = [0, -15];
 UPS_Z      = -39;     // standoff tops
 module ups_18650() translate([UPS_CENTRE[0], UPS_CENTRE[1], UPS_Z]) {
    color("#202020") difference() {
        translate([-89/2, -22/2, 0]) cube([89, 22, 1.6]);
        for (m = [-1, 1]) translate([m * 27.9, 0, -1]) cylinder(d = 3, h = 4);
    }
    color("#151515") translate([-77/2, -21/2, 1.6]) difference() {
        cube([77, 21, 22.4 - 1.6]);
        translate([3, 1.5, 3]) cube([71, 18, 30]);
    }
    color("#4060c0") translate([-65/2, 0, 1.6 + 3 + 18.5/2]) rotate([0, 90, 0]) cylinder(d = 18.5, h = 65);
    color("#b0b0b0") translate([89/2 - 7, -4.5, 1.6]) cube([7.5, 9, 3.2]);   // Type-C
 }
 // Small USB-C breakout (owner: glued in the holder at the side port), on the
 // port block (u 88..99, v -10..4, top Z -28) with the receptacle facing the
 // opening (v -10..4, Z -35..-20). Board size approximate.
 module usb_c_breakout() translate([88, -10, -28]) {
    color("#1a3a8a") cube([11, 14, 1.6]);
    color("#c0c0c0") translate([11 - 7.3, 7 - 8.9/2, 1.6]) cube([7.5, 8.9, 3.2]);
 }
 // IMU (owner: on the big standoff in the middle), assumed a GY-521 / MPU6050
 // like the robot's: 21.2 x 15.6 mm board on the 21 x 9 mm block (top Z -17),
 // its hole end over the block's two d3 holes at v 35, board towards the centre.
 module imu_gy521() translate([0, 35 + 3.5 - 15.6, -17]) {
    color("#1f4fa0") translate([-21.2/2, 0, 0]) cube([21.2, 15.6, 1.6]);
    color("#222") translate([-2, 7, 1.6]) cube([4, 4, 1]);
 }
 // Teensy 4.0 (owner; no mounting holes), assumed on the hole-less 8 x 24 mm
 // block (u -4..4, v 44..68, top Z -17). Across the block by default; lengthwise
 // it would end 0.1 mm from the shell wall.
 TEENSY_LENGTHWISE = false;
 module teensy_4_0() translate([0, 56, -17]) rotate([0, 0, TEENSY_LENGTHWISE ? 90 : 0]) {
    color("#1e5a2a") translate([-35.6/2, -17.8/2, 0]) cube([35.6, 17.8, 1.6]);
    color("#222") translate([-3, -5, 1.6]) cube([10, 10, 1.2]);                       // i.MX RT1062
    color("#c0c0c0") translate([-35.6/2 - 1, -7.5/2, 1.6]) cube([5.7, 7.5, 2.9]);    // micro-USB
 }
 module remote_assembly() {
    if (SHOW_BOTTOM) color("#3a3a3a") remote_bottom();
    if (SHOW_LID) translate([0, 0, EXPLODE]) color("#5a5a5a") remote_lid();
    if (SHOW_DISPLAY) translate([0, 0, EXPLODE]) nextion_3_5();
    if (SHOW_BATTERY) ups_18650();
    if (SHOW_BATTERY) usb_c_breakout();
    if (SHOW_BATTERY) imu_gy521();
    if (SHOW_BATTERY) teensy_4_0();
    // pots towards the nearest side wall and the near edge, where there's room
    if (SHOW_STICKS) for (s = STICKS) translate([s[0], s[1], LID_Z[1] + EXPLODE])
        mirror([s[0] < 0 ? 1 : 0, 0, 0]) jh_d400x();
 }
 remote_assembly();
@@ -0,0 +1,36 @@
 // The whole 2026 hexapod: body (body.scad) plus six legs (leg.scad),
 // placed and posed like robot/Config.h. Robot frame: +X forward (switch
 // end), +Y left, +Z up, Z = 0 on the bottom plate's top face.
 use <body.scad>
 use <leg.scad>
 /* [Pose] */
 // "original" = the Fusion model's pose; "stand" = firmware stance
 // (Kinematics::neutralStance(): feet 130 mm out, 150 mm down).
 POSE_NAME = "stand"; // [original, stand]
 // Optional per-leg override, [coxa, femur, tibia] in degrees, legs 0..5.
 POSE_OVERRIDE = [];
 // Leg mounts from robot/Config.h: x, y, mount angle (0..2 right, 3..5 left).
 // Hexagon layout: corner legs 60 deg round from the mid legs.
 LEG_MOUNT = [[100, -50, -30], [0, -65, -90], [-100, -50, -150],
             [-100, 50, 150], [0, 65, 90], [100, 50, 30]];
 JOINT_PLANE_Z = 13.5;   // femur/knee axes, halfway up the body cavity
 POSES = [["original", [0, 0, -90]], ["stand", [0, -1.2, -98.3]]];
 function base_pose() = [for (p = POSES) if (p[0] == POSE_NAME) p[1]][0];
 function leg_pose(i) = len(POSE_OVERRIDE) == 6 ? POSE_OVERRIDE[i] : base_pose();
 module robot() {
    body_assembly();
    for (i = [0:5]) {
        m = LEG_MOUNT[i];
        p = leg_pose(i);
        translate([m[0], m[1], JOINT_PLANE_Z])
            if (m[2] > 0) rotate([0, 0, m[2]]) leg(p);
            else mirror([0, 1, 0]) rotate([0, 0, -m[2]]) leg([-p[0], p[1], p[2]]);
    }
 }
 robot();
@@ -0,0 +1,28 @@
 // Hitec HS-485HB, from the servo's Fusion model (servo-hitec-hs-485hb).
 // Local frame: shaft on the Z axis, case extending +X, Z = 0 at the ear
 // underside. Include (not use) this file to get the constants.
 SERVO_CASE      = [[-10, -10, -28], [30, 10, 9.75]];
 SERVO_EARS      = [[-16, -10, 0], [36, 10, 3]];
 SERVO_EAR_HOLES = [[-13.9, 5], [-13.9, -5], [34.35, 5], [34.35, -5]];
 SERVO_EAR_SCREW_D = 2.5;   // pilot hole for the ear screws in printed parts
 POCKET_CLEAR    = 0.5;
 module servo_pocket_2d() {
    translate([SERVO_CASE[0][0] - POCKET_CLEAR, SERVO_CASE[0][1] - POCKET_CLEAR])
        square([SERVO_CASE[1][0] - SERVO_CASE[0][0] + 2*POCKET_CLEAR,
                SERVO_CASE[1][1] - SERVO_CASE[0][1] + 2*POCKET_CLEAR]);
    for (h = SERVO_EAR_HOLES) translate(h) circle(d = SERVO_EAR_SCREW_D);
 }
 module hs485hb() {
    color("#303030") {
        translate(SERVO_CASE[0]) cube(SERVO_CASE[1] - SERVO_CASE[0]);
        difference() {
            translate(SERVO_EARS[0]) cube(SERVO_EARS[1] - SERVO_EARS[0]);
            for (h = SERVO_EAR_HOLES) translate([h[0], h[1], -1]) cylinder(d = 4.42, h = 5);
        }
        translate([0, 0, 9.75]) cylinder(d = 14, h = 2.25);
    }
    color("#e0e0e0") translate([0, 0, 12]) cylinder(d = 5, h = 3.25);
 }
@@ -9,12 +9,19 @@
 // ---- Leg geometry ----
 // Taken from the Unity model (Hexapod_Simulation_Unity/Assets/Main.unity,
 // 1 Unity unit = 10 mm): hip pivots at x = +-10 / 0, z = +-5 / +-6.5;
-// coxa 5.5, femur 10, tibia 15. BENCH: confirm against the real chassis.
+// coxa 5.5, femur 10, tibia 15. Confirmed exactly against the real
 // chassis's CAD (hardware/openscad, from the Fusion model): coxa axes at
 // these mounts, coxa 55 / femur 100 / tibia 150 mm to the centre of the
 // 10 mm foot ball. The femur and knee axes lie in the coxa pivot plane
 // (Z = 0), 13.5 mm above the bottom plate's top face.
 constexpr int NUM_LEGS = 6;
 // Leg order: 0=front-right, 1=mid-right, 2=rear-right, 3=rear-left, 4=mid-left, 5=front-left
 // Angles measured counterclockwise from the body's +X (forward) axis, viewed from above.
-// This is the direction the coxa points at servo center: straight sideways on this chassis.
+// This is the direction the coxa points at servo center. Hexagon layout (owner's
-constexpr float LEG_MOUNT_ANGLE_DEG[NUM_LEGS] = { -90, -90, -90,  90,  90,  90 };
+// request): mid legs straight sideways, front/rear legs 60 deg further round, so
 // all six are 60 deg apart. BENCH: the corner coxa brackets sit 60 deg round on
 // their servo splines (4 teeth of 24) compared with the old sideways layout.
 constexpr float LEG_MOUNT_ANGLE_DEG[NUM_LEGS] = { -30, -90, -150, 150, 90, 30 };
 constexpr float LEG_MOUNT_X_MM[NUM_LEGS]      = { 100,   0, -100, -100,  0, 100 };
 constexpr float LEG_MOUNT_Y_MM[NUM_LEGS]      = { -50, -65,  -50,   50,  65,  50 };
@@ -23,7 +30,19 @@ constexpr float FEMUR_LEN_MM = 100.0f;
 constexpr float TIBIA_LEN_MM = 150.0f;
 // ---- Joint limits, degrees ----
-constexpr float COXA_MIN_DEG  = -60,  COXA_MAX_DEG  = 60;
+// Physical limits from the OpenSCAD model (hardware/openscad, collision
 // sweep of the real parts, see PLANNING.md "Physical limits"), and servo
 // travel (+-90 coxa/femur, -180..0 tibia):
 //   coxa  mid legs          -66.5 .. 66.5   coxa bracket shell hits the plate
 //   coxa  0 front-right, 3 rear-left   -95.75 .. 66.75 (servo: -90)
 //   coxa  2 rear-right, 5 front-left   -66.75 .. 95.75 (servo: 90)
 //   femur                  -101 .. 101   femur link hits the coxa bracket (servo: 90)
 //   tibia                  -177 .. 12.75 rod folds into the femur link / shell hits it (servo: 0)
 // The limits below keep ~3 deg from those and the earlier software limits
 // where those are tighter. Per leg, because the corner legs' ranges differ (in
 // the old sideways layout they could only swing ~36 deg towards the mid leg).
 constexpr float COXA_MIN_DEG[NUM_LEGS] = { -60, -60, -60, -60, -60, -60 };
 constexpr float COXA_MAX_DEG[NUM_LEGS] = {  60,  60,  60,  60,  60,  60 };
 constexpr float FEMUR_MIN_DEG = -80,  FEMUR_MAX_DEG = 80;
 constexpr float TIBIA_MIN_DEG = -150, TIBIA_MAX_DEG = -20;
@@ -41,8 +60,10 @@ constexpr float STANCE_HEIGHT_RATE_MM_S = 60.0f;
 // ---- Leg collision ----
 // Minimum distance between the center lines of neighbouring legs' segments
 // (coxa, femur, tibia). Gait strides and body poses are scaled down to keep
-// it. BENCH: set to roughly the width of a leg (servo body + bracket).
+// it. From the OpenSCAD model: at the joints a leg reaches 33.7 mm to its
-constexpr float LEG_CLEARANCE_MM = 30.0f;
+// horn side (rear) and 21.5 mm to its bearing side (front), so two
 // neighbours touch at 55.2 mm between center lines.
 constexpr float LEG_CLEARANCE_MM = 56.0f;
 // ---- Servos (Teensy 3.6, hardware PWM at SERVO_PWM_HZ) ----
 // One entry per servo: pulse = us_at_0deg + us_per_deg * joint_deg, clamped
@@ -51,7 +51,7 @@ JointAngles Kinematics::solve(int i, const FootTarget& target) {
  out.femur_deg = degrees(femur_rad);
  out.tibia_deg = degrees(tibia_rad);
-  if (out.coxa_deg  < COXA_MIN_DEG  || out.coxa_deg  > COXA_MAX_DEG)  out.valid = false;
+  if (out.coxa_deg  < COXA_MIN_DEG[i] || out.coxa_deg  > COXA_MAX_DEG[i]) out.valid = false;
  if (out.femur_deg < FEMUR_MIN_DEG || out.femur_deg > FEMUR_MAX_DEG) out.valid = false;
  if (out.tibia_deg < TIBIA_MIN_DEG || out.tibia_deg > TIBIA_MAX_DEG) out.valid = false;
@@ -40,13 +40,14 @@ HXSIM_API void hxsim_get_geometry(HxGeometry* g) {
    g->mount_x_mm[i] = LEG_MOUNT_X_MM[i];
    g->mount_y_mm[i] = LEG_MOUNT_Y_MM[i];
    g->mount_angle_deg[i] = LEG_MOUNT_ANGLE_DEG[i];
    g->coxa_min_deg[i] = COXA_MIN_DEG[i];
    g->coxa_max_deg[i] = COXA_MAX_DEG[i];
  }
  g->coxa_mm = COXA_LEN_MM;
  g->femur_mm = FEMUR_LEN_MM;
  g->tibia_mm = TIBIA_LEN_MM;
  g->stance_radius_mm = STANCE_RADIUS_MM;
  g->stance_height_mm = STANCE_HEIGHT_MM;
  g->coxa_min_deg = COXA_MIN_DEG;   g->coxa_max_deg = COXA_MAX_DEG;
  g->femur_min_deg = FEMUR_MIN_DEG; g->femur_max_deg = FEMUR_MAX_DEG;
  g->tibia_min_deg = TIBIA_MIN_DEG; g->tibia_max_deg = TIBIA_MAX_DEG;
  g->control_hz = CONTROL_HZ;
@@ -18,7 +18,7 @@
 #endif
 // Bump whenever a signature or struct below changes; the C# side checks it.
-#define HXSIM_API_VERSION 6
+#define HXSIM_API_VERSION 7
 #define HXSIM_NUM_LEGS 6
@@ -30,7 +30,8 @@ typedef struct {
  float mount_angle_deg[HXSIM_NUM_LEGS];
  float coxa_mm, femur_mm, tibia_mm;
  float stance_radius_mm, stance_height_mm;
-  float coxa_min_deg, coxa_max_deg;
+  float coxa_min_deg[HXSIM_NUM_LEGS];   // per leg: corner legs can't swing far towards the mid leg
  float coxa_max_deg[HXSIM_NUM_LEGS];
  float femur_min_deg, femur_max_deg;
  float tibia_min_deg, tibia_max_deg;
  float control_hz;
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